New study examines experience with speed limits in 10 countries

The study examined how the road safety performance in 10 countries changed after they changed speed limits or introduced automatic speed cameras on a large scale.

All the cases indicated a strong relationship between speed and the number of crashes: An increase in mean speed was accompanied by a higher number of crashes and casualties. A decrease was associated with fewer crashes and casualties. In no case did an increase in mean speed coincide with fewer crashes or casualties.

These results confirm the existing scientific evidence that speed has a direct influence on the occurrence of traffic crashes and on their severity.

According to a widely used scientific formula, every 1 per cent increase in average speed results in a 2 per cent increase in all injury crashes, a 3 per cent rise in fatal and severe crashes and 4 per cent more fatal crashes.

Thus, reducing speed by a few km/h can greatly reduce the risks of and severity of crashes.

The report recommends to:

• reduce the speed on roads as well as speed differences between vehicles; • set speed limits based on the Safe System principles, i.e. at a level that humans can survive without dramatic consequences in case of a crash; • introduce compensation measures where speed limits are increased; for instance, stricter enforcement or a safety upgrade of the road infrastructure; • use automatic speed control to effectively reduce speed.

Working towards a Safe System, the authors propose as reasonable speed limits:

• 30 km/h in built-up and residential urban areas where motorized vehicles and vulnerable road users share the same space; • 50 km/h in other urban areas with intersections and high risk of side collisions; • 70 km/h on rural roads without a median barrier and a risk of head-on collisions.